/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 26727
 * Date: 2024-02-26
 * Time: 9:55
 */
public class BinarySearchTree {
    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    TreeNode root = null;

    //查找二叉搜索树的指定的val值
   public TreeNode find(int val) {
       TreeNode cur = root;
       while (cur != null) {
           if(cur.val < val) {
               cur = cur.right;
           }
           else if(cur.val == val) {
               return cur;
           }
           else {
               cur = cur.left;
           }

       }
       return null;
   }

   //插入
    public void insert(int val) {
       if(root == null) {
           root = new TreeNode(val);
           return;
       }

       TreeNode cur = root;
       TreeNode parent = null;

       while(cur != null) {
           if(val > cur.val) {
               parent = cur;
               cur = cur.right;
           }else if(val < cur.val) {
               parent = cur;
               cur = cur.left;
           }else {
               return;
           }
       }
        TreeNode node = new TreeNode(val);
       if(parent.val < val) {
           parent.right = node;
       }else {
           parent.left = node;
       }
    }

    //中序遍历
    public void inorder(TreeNode root) {
       if(root == null) {
           return;
       }
       inorder(root.left);
       System.out.print(root.val+" ");
       inorder(root.right);
    }


    //删除
    public void remove(int val) {
       TreeNode cur = root;
       TreeNode parent = null;
       while(cur != null) {
            if(cur.val == val) {
                removeNode(parent,cur);
                return;
            }else if(cur.val < val) {
                parent = cur;
                cur = cur.right;
            }else {
                parent = cur;
                cur = cur.left;
            }
       }
    }

    private void removeNode(TreeNode parent,TreeNode cur) {
       if(cur.left == null) {
           if(cur == root) {
               root = cur.right;
           }else if(parent.left == cur) {
               parent.left = cur.right;
           }else {
               parent.right = cur.right;
           }
       }else if(cur.right == null) {
           if(cur == root) {
               root = cur.left;
           }else if(parent.left == cur) {
               parent.left = cur.left;
           }else {
               parent.right = cur.left;
           }
       }else {
            TreeNode target = cur.right;
            TreeNode targetParent = cur;
            while(target.left != null) {
                targetParent = target;
                target = target.left;
            }
            //经常忘记替换 删除的关键 替换法
            cur.val = target.val;
            if(target == targetParent.left) {
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }
       }
    }




































}
